A central aspect of Kant’s Transcendental Dialectic is his claim that there are concepts – the transcendental ideas – that necessarily arise from rational reflection. According to Kant, these ideas of reason, like the categories of the understanding, form an a priori system. In Chapter 6, we first look at Kant’s conception of transcendental ideas and survey the system they form. Next, it is argued that Kant does not attempt to derive the transcendental ideas in questionable ways from the forms of rational inferences or the possible relations between subject, object, and representation (even though the text suggests this), but rather considers them, much more plausibly, as concepts we arrive at through rational inferences about specific (psychological, cosmological, and theological) subject matters. The central philosophical point here is that concepts can be the result of (what Kant calls) ‘necessary inferences of reason.’ A first instance of this is Kant’s derivation of the concept of the unconditioned; the chapter then turns to the three classes of transcendental ideas (psychological, cosmological, theological).

The Introduction explains the two major aims of the book. First, the book will offer a novel interpretation of the Transcendental Dialectic that isolates its constructive side, Kant’s account of the rational sources of speculative metaphysics (concerning the soul, the world as a whole, and God), and distinguishes it clearly from its destructive side, Kant’s critique of this kind of metaphysics. Second, it will reconstruct, and where possible defend, a Kantian account of the rational sources of metaphysical thinking. In particular, it will argue that Kant is right in claiming that metaphysical speculation arises naturally out of principles that guide us in everyday rational thought. As the book will argue, Kant gives us good reason to think that discursivity, iteration, and striving for completeness are fundamental features of rational thinking and that, taken together, they give rise to a specific kind of metaphysical speculation. This is a distinctive and original perspective on metaphysics that deserves to be taken seriously in the current metaphysical and meta-metaphysical debates.